Or lowering apparatus



(No Model.) 3 Sheets-Sheet 1. T. H. & E. GARDNER. RETAINING 0R LOWERING APPARATUS. No. 519,110.

Patented May 1,1894.

3 Sheets-Sheet 2.

(No Model.)

T. H. 86 E; GARDNER. RETAINING 0R LOWE-RING APPARATUS. No. 519,110. Patented May 1,1894.

[h mn (No Model.) a Sheets-Sheet 3. T. H. 813 E. GARDNER. RETAINING OR LOWERING APPARATUS. NO. 519,110.

Patented May 1,1894.

fifibmssaz NITED STATES PATENT FFICE.

THOMAS HARRY GARDNER AND EDWARD GARDNER, OF MANCHESTER,

' ENGLAND.

SPECIFICATION forming part of Letters Patent No. 519,110, dated May 1, 1894.

Application filed November 20, 1893. Serial No. 1i4=24 (N modBl Patented in 3115194115 August in France December 26,1892, No. 226,674.

1892, lie-14,508, and

To all whom it may concern.-

Beit known that we, THOMAS HARRY GAR NER and EDWARD GARDNER, engineers, subjects of the Queen of Great Britain, both residing at Hadfield Street, Cornbrook, Manchester, England, have invented certain new and useful improvements in retaining or a stationary cylindrical surface.

lowering apparatus applicable to dental and other chairs and to other uses, (for which we have received Letters Patent in Great Britain,

.No. 14,508, dated August 11, 1892, and in France, No. 226,674, dated December 26, 1892,) of which the following is a specification.

This invention relates to a dental chair such as is described in the specification of our former patent, datedJuly 26, 1892, No. 479,415, and has for its object improved mechanism applicable to lowering the chair seat.

In the dental chair to which the, invention is applicable there is a fixed chair standard; an intermediate moving part sliding on the fixed standard up and down, and anupper moving part sliding upon the intermediate part and carrying the chair seat. These parts are in all respects as described in our said former patent. On the intermediate part two shafts geared together are provided and on the shafts are toothed wheels. These wheels engage with. racks upon the chair standard and upon, the upper moving part. The lowering of the chair seat is controlled by a wheel which is geared with the descending parts. On the wheel are frictional looking levers which are held by springs against The friction thus established is sufficient to prevent movement. If howeverthe wheel be rotated by the hand, centrifugal force removes the locking levers from the stationary surface. If the speed of descent tends to become excessive the centrifugal force causes a further movement of the locking levers and this movecordance with our invention. The seat in this figure is represented in its lower position. is a side elevation of the same chair with the seat in its raised position. The back of the chair is not represented in this figure. Figs. 4. and 5 are sectionalviews of parts of the lowering gear. Figs. 6 to 10 are intended to illustrate, by detail views, thetelescopic framing of the chair; Fig. 6 is asectioual elevation.

Fig. 7 is a rear elevation. Fig. 8 is a horizontal section; and Figs. 9 and 10 are vertical sections.

'A is the fixed chair standard. Bis the intermediate standard or moving part sliding Fig.2 is a view of the foot rest. Fig. 3 it i on the fixed standard up and down; and Ois the upper moving part sliding upon the intermediate part and carrying the chair seat. These three parts are so geared by racks and pinions, that, for every increment of rise given to B, the intermediate part, the upper part 0 rises a corresponding increment in relation to the intermediate part. Consequently, in relation to the fixed standard, the upper moving part 0 rises and falls twice as fast as the intermediate moving part B. To this end the part A has rack teeth upon it at a a and the part C at c c. The intermediate part carries two parallel spindles Z7 19 which are geared together by the wheels 5 b and carry pinions 6 b 6 b engaged with the racks a and 0, respectively.

The descent of the chair seat is prevented by the worm wheel is, (Fig. 7,) which engages with and is locked by the screw or worm Z.

The worm wheel is is not fast upon the spinthe worm are so inclined that, when left free,

the worm will revolve and allow the load to run down. This however is prevented by the mechanism shown by Figs. land 5. m is the axis of the worm; it passes through the stationary cylindrical boss 'n and has keyed upon it the hand wheel 0. Pivoted upon or within the hand wheel are the centrifugal upon the brake pieces to hold them against a 5 stationary cylindrical surface when the wheel is at rest and prevent any movement being locking levers p p and springs 19 p fixed to the levers and abutting upon the flange of the wheel, press the locking levers inward so that the shoulders n p upon the levers bear upon the cylindrical surface of the boss at. The resistance thus ofiered is sufficient to prevent the wheel 0 being started from rest by any pressure brought upon the worm through the worm wheel, nevertheless the wheel can readily be turned by hand and then the centrifugal force moves the locking levers outward sufficiently to lift the shoulders 19 19* from the surface of the boss at; consequently movement once started continues until the chair is run down or the wheel 0 is stopped by the hand. If the speed should tend to accelerate unduly, the centrifugal force so far overpowers the springs p 19' that the shoulders 19 19 at the extremities of the locking levers 10 are brought to bear upon the boss n and to offer a resistance by which the acceleration is checked.

We claim as our invention 1. The retaining and lowering gear herein described comprising a movable section or part to be raised, a shaft m, a worm upon it gearing into aworm wheel which is geared with the part to be raised or lowered,a wheel fast upon the shaft, weighted brake pieces pivoted upon the wheel, a stationary cylindrical surface for the brake pieces to act against when the wheel is revolved too fast, and springs acting upon the brake pieces to hold them against a stationary cylindrical surface when the wheel is at rest and prevent any movement being given to the shaft through the gearing.

2. The retaining and lowering gear herein described comprising a movable section or part to be raised, a shaft m, a worm upon it gearing into a worm wheel which is geared with the part to be raised or lowered, a wheel fast upon the shaft, weighted brake pieces pivoted upon the wheel, and springs acting given to the shaft through the gearing.

3. The combination of the stationary and movable sections of the chair, a shaft mounted on one of the sections and geared with the other sections, a flanged wheel secured to the shaft, brake pieces pivoted to the wheel, springs operating upon the brake pieces, and a stationary boss having a cylindrical surface with which the brake pieces are adapted to engage both when the wheel is at rest and when it is revolved at too high a speed, substantially as described.

4. The retaining and lowering gear herein described comprising the part to be raised or lowered, a shaft having upon it a worm geared with the part to be raised or lowered, a wheel secured to the shaft, weighted brake pieces pivoted to the wheel, a stationary cylindrical surface for the brake pieces on one side of their pivots to act against when the wheel is revolved too fast, and springs acting upon the brake pieces to cause them to act on the opposite side of their pivots, upon the stationary cylindrical surface when the wheel is at rest.

5. The retaining and lowering gear herein described, comprising the part to be raised or lowered, a shaft geared with the part to be raised or lowered, a Wheel secured to the shaft, weighted brake pieces pivoted to the wheel, springs operating upon the brake pieces, a boss having a cylindrical surface with which the brake pieces are adapted to engage on either side of their pivots, substantially as described.

THOMAS HARRY GARDNER. EDWARD GARDNER.

Witnesses:

HERBERT BAMFORD, SAMUEL E. KIRK. 

